Add notification groups

### Your use case

#### What would you like to do?
It would be great if you could define notification groups.

#### Why would you like to do it?
Since Matrix is a replacement for several messenger, the needs for notifications differ.
When i am on my mobile device, i don't want to get notification for some Rooms.

#### How would you like to achieve it?
Notfication Groups in the settings
The question is, how you set the notification for this groups in the rooms
On solution could be making checkboxes beside this
(only if you activate notification groups of course)
Another solution could be that you can only set the notifications settings with devices which are in the group.

### Have you considered any alternatives?

_No response_

### Additional context

_No response_